Understanding your glucose levels and how they’re measured

Thursday, 26 August 2021

There is a difference between your glycated haemoglobin (HbA1c) and blood glucose levels. Understanding what those two measurements are is an important step towards using the tools that will help you keep your glucose levels in a healthy range.

Like any other job, living well with diabetes requires you to have the right tools and know how to use them well. The two main options available to you for evaluating managing your health are glycated haemoglobin (HbA1c) and self-monitoring blood glucose. Both are important for managing your diabetes; however, they will give you different views of blood glucose levels.

Glycated haemoglobin (HbA1c)

Your annual pathology results will include a glycated haemoglobin (HbA1c). It is the amount of glucose that sticks to your red blood cells. The life span of your red blood cells is 90- 120 days. For this reason, HbA1c will only significantly change every three months. Glycated haemoglobin (HbA1c) is shown on your blood results as being measured as a percentage or mmol/mol. An example of another equivalent measure is centimetres and inches.

As you can see by the table below, neither glycated haemoglobin (HbA1c) represented with percentage or mmol/mmol are the same numbers as the average of blood glucose levels, measured in mmol/L. Glycated haemoglobin (HbA1c) will not tell you what your blood glucose levels are at any one point.

 

So, at the same glycated haemoglobin (HbA1c), you may have smaller rises and falls of blood glucose or higher highs and lower lows.

Glycated haemoglobin (HbA1c) is helpful to help you and your doctor to decide on management strategies. If there is no reason for your readings to fluctuate or you have no safety concerns around blood glucose levels, a glycated haemoglobin (HbA1c) may be the only measurement you require to manage your diabetes.

Blood glucose monitoring

If you use blood glucose monitoring, know what the readings represent and act on the readings. The table below is a guide to monitoring.

Why I am monitoring When I am monitoring What the readings could tell me
Mealtime Before and two hours after your start eating a meal. If the amount of carbohydrate in my meal was suitable or whether I have enough insulin releasing from my pancreas.
Fasting First in the morning before eating, drinking or exercising. How much glucose is flowing from my storage in my liver, and if I have enough insulin to use this glucose. A starting point for my day.
Exercise Before, during and after exercise. A drop in readings may be encouraging. To ensure my levels are safe for exercise if I am using insulin.
Sick days Every two hours. To know when to follow my sick day management plan. To know when I might need help.
Symptoms When required. To act on immediate action on hypoglycaemia or hyperglycaemia.
Driving Before driving and every two hours on long trips. To know I am safe to drive when I take medication which may cause hypoglycaemia eg insulin or sulfonylurea tablets.

 

If your levels are rising over time, take action. If this is a gradual rise in post-meal or fasting readings, consult your doctor. The occasional reading above your target range is not important, especially if you know why.

However, take immediate action on any readings below 4mmol/l: this is hypoglycaemia. Treat the low blood glucose with some quickly digested carbohydrate such as 5-6 glucose jelly beans.

If you’re unwell, use your readings to follow your sick day management plan. Your doctor can help you make a sick day management plan around your fluid intake, medications and when to seek medical attention.

If your readings are steady and on target, you may monitor less frequently.

If you are a person who eats about the same every day, you would not monitor around meals.

When your lifestyle or medication changes, increase monitoring until your levels are steady.

To summarise:

  • Know what the reading represents compared to your target range.
  • Know what to do at that blood glucose level.
  • Only monitor when you are going to act on that reading.
  • Increase and decrease monitoring according to lifestyle and medication.

If you have any questions, please contact us via email on info@ndss.com.au or call the NDSS Helpline on 1800 637 700.

By Donna Itzstein, Pharmacist, CDE

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